A new study shows that, as a person gets older, having a healthy pair of lungs helps maintain “fluid” reasoning — the ability to think logically and solve problems in novel situations, independent of previous knowledge.

However, poor lung health did not appear to harm memory or lead to any significant loss of stored knowledge, according to the research published in the journal Psychological Science.

Ohio State University researchers used data from a Swedish study of aging that followed participants’ health for almost two decades. An analysis determined that reduced lung function can lead to cognitive loss but that problems with cognition do not affect lung health.

“The logical conclusion from this is that anything you could do to maintain lung function should be of benefit to fluid cognitive performance as well,” said lead author Charles Emery, Ph.D., professor of psychology at Ohio State.

“Maintaining an exercise routine and stopping smoking would be two primary methods. Nutritional factors and minimizing environmental exposure to pollutants also come into play.”

The study offers insight into the process of human aging. While one theory of aging suggests that all functions slow down at the same rate, this study shows that some aspects of functional decline contribute to a change in the rate of other areas of decline.

“In this case, pulmonary functioning may be contributing to other aspects of functioning,” Emery said. “It starts to speak to the bigger question: What are the processes involved in aging?”

The study sample included 832 participants between ages 50 and 85 who were assessed in up to seven waves of testing over 19 years as part of the Swedish Adoption/Twin Study of Aging. The researchers used data from pulmonary and cognitive tests conducted in the Swedish study.

They measured lung function in two ways: forced expiratory volume, or how much air a person can push out of the lungs in one second, and forced vital capacity, the volume of air that is blown out after a deep inhalation.

“We were looking for effects in both directions. We had previously looked in simpler models and found that pulmonary function did predict cognitive function, but there are some studies that show the opposite direction. It was important for us to go into this with an open mind and use this modeling to test both directions,” Emery said.

The study also showed that changes in cognitive function did not predict lung outcomes.

“In these models the relationship is consistently moving from pulmonary function to cognitive function and not the other way,” said Emery, also a professor of internal medicine and an investigator in Ohio State’s Institute for Behavioral Medicine Research.

“We know, for example, that the speed at which people can perform the processing task does decline with age. But now we have data that suggests pulmonary function actually predicts that decline,” he said.

The researchers speculate that reduced lung health could lower the availability of oxygen in the blood which might affect chemicals that transmit signals between brain cells.